## Zidan Sun* , Xiaofeng Zhou** , Likai Liang* and Yang Mo*## |

Time (s) | Resistance [TeX:] $$(\Omega)$$ | Reactance[TeX:] $$(\Omega)$$ | Susceptance[TeX:] $$\left(\times 10^{-3} \mathrm{S}\right)$$ |
---|---|---|---|

0 | 6.0937 | 49.0941 | 0.4512 |

5 | 6.0874 | 49.0613 | 0.4509 |

10 | 6.1058 | 49.0173 | 0.4510 |

15 | 6.1163 | 48.9674 | 0.4508 |

20 | 6.1400 | 49.0084 | 0.4510 |

25 | 6.1338 | 48.9493 | 0.4510 |

30 | 6.1490 | 49.0507 | 0.4514 |

35 | 6.1061 | 49.1011 | 0.4513 |

A case study of a 220kV transmission line named Yuxin Line from Gangyu Station to Xingang Station in Yantai is conducted. The parameter information of the transmission line is shown in Table 2. The theoretical value of parameters is [TeX:] $$\mathrm{R}=3.95 \Omega, \mathrm{X}=20.8 \Omega, \mathrm{B}_{1}=68.325 \mu \mathrm{S},$$ which is set as the base case. The test time is from 21:00 to 22:00. The sampling interval is 5 minutes and there are 12 groups of samples.

Table 2.

Line parameters | Information |
---|---|

Line name | Yuxin Line |

The first station | Gangyu Station |

The last station | Xingang Station |

Voltage level (kV) | 220 |

Line type | LGJ-400 |

Line length (km) | 50 |

Unit resistance [TeX:] $$(\Omega)$$ | 0.079 |

Unit reactance [TeX:] $$(\Omega)$$ | 0.416 |

Unit susceptance [TeX:] $$(\mu \mathrm{S})$$ | 2.733 |

Unit specific heat [TeX:] $$\left(\mathrm{J} /\left(\mathrm{km} \cdot^{\circ} \mathrm{C}\right)\right)$$ | 1127 |

Safety current (A) | 845 |

Table 3.

Sampling point | Full-parameter online estimation | Independent resistance online estimation | ||||
---|---|---|---|---|---|---|

Resistance [TeX:] $$(\Omega)$$ | Reactance[TeX:] $$(\Omega)$$ | Susceptance[TeX:] $$(\mu \mathrm{S})$$ | Resistance[TeX:] $$(\Omega)$$ | Reactance[TeX:] $$(\Omega)$$ | Susceptance[TeX:] $$(\mu \mathrm{S})$$ | |

1 | 4.3729 | 19.3273 | 68.431 | 4.2890 | 20.8000 | 68.325 |

2 | 4.2335 | 18.8677 | 68.376 | 4.4395 | 20.8000 | 68.325 |

3 | 4.4231 | 19.3496 | 68.302 | 4.3859 | 20.8000 | 68.325 |

4 | 4.3804 | 18.5730 | 68.412 | 4.4086 | 20.8000 | 68.325 |

5 | 4.2799 | 19.9671 | 68.297 | 4.3275 | 20.8000 | 68.325 |

6 | 4.4238 | 18.7734 | 68.288 | 4.5064 | 20.8000 | 68.325 |

7 | 4.2803 | 18.5423 | 68.305 | 4.2076 | 20.8000 | 68.325 |

8 | 4.2640 | 17.9758 | 68.349 | 4.1098 | 20.8000 | 68.325 |

9 | 4.3346 | 17.9857 | 68.286 | 4.4683 | 20.8000 | 68.325 |

10 | 4.3709 | 19.3020 | 68.376 | 4.2279 | 20.8000 | 68.325 |

11 | 4.4555 | 19.4563 | 68.478 | 4.4203 | 20.8000 | 68.325 |

12 | 4.3644 | 19.8603 | 68.455 | 4.3068 | 20.8000 | 68.325 |

Firstly, online estimation of full parameters is achieved by the proposed method in this paper. The result of full-parameter estimation is shown in the left part of Table 3, and there are 12 sampling points. The maximum difference between the actual value and the theoretical value of the resistance is 0.5055 at the 11th sampling point, and the maximum difference between the actual value and the theoretical value of the reactance is 2.8242 at the 8th sampling point.

Then, the resistance is estimated independently online while the reactance and the susceptance are set to be the theoretical value. The results of independent resistance estimation based on SCADA are shown in the right part of Table 3. Fig. 3 further describes online estimation results of the resistance under the two methods. It can also be seen from Table 3 and Fig. 3 that the maximum difference of resistance between full-parameter estimation and independent resistance estimation is 0.206 at the 2nd sampling point, which accounts for 4.8% of the total resistance. The difference does exist and it is necessary to be considered. This further illustrates the necessity of the full-parameter online estimation. The full parameter estimation of the resistance will be more appropriate with the actual operation of transmission lines.

A 5-bus power system is taken as the example. The transmission line type is LGJ-400/50, and the voltage level is 220 kV. The conductor diameter is 27.63 mm. The phase sequence is horizontal arrangement, and the spacing is 8 m. The height of the line to ground is 10 m. The lengths of branch 1– 2, 2–3, and 1–3 are all 50 km. The electromagnetic environment indicator A is the midpoint of branch 2– 3. The network structure is shown in Fig. 4.

Based on the online estimation results of transmission line parameters in Section 3.2, the electromagnetic environment of alternating current transmission lines is obtained. The theoretical value of parameters is set as the base case. The result of full-parameter estimation at the 11th sampling point is set as the case 1, and the result of independent resistance estimation at the 6th sampling point is set as the case 2. The line parameters of three cases are shown in Table 4.

Table 4.

Resistance () | Reactance () | Susceptance [TeX:] $$(\mu S)$$ | Voltage [TeX:] $$(k V)$$ | Current (A) | |
---|---|---|---|---|---|

Base case | 3.9500 | 20.8000 | 68.325 | 228.8 | 43.94 |

Case 1 | 4.4555 | 19.4563 | 68.478 | 228.8 | 44.58 |

Case 2 | 4.5064 | 20.8000 | 68.325 | 228.8 | 44.55 |

The results of voltage and current are obtained, and then the electromagnetic environment surrounding the line is analyzed. The voltage magnitudes at point A under the three cases are all 1.04 p.u., so that the electric field intensity of three cases are close. For the currents at point A under the three cases, base case is 43.94 A, case 1 is 44.58 A, and case 2 is 44.55 A. The magnetic field intensity of three cases are different. The height of calculation point to ground is 1.5 m. The horizontal range is between -20 m and +20 m. The magnetic field intensity is calculated every 0.01 m horizontal distance. The distribution curves of the magnetic field intensity distribution at point A is shown in Fig. 5.

The curves are distributed unimodally, presenting lateral attenuation trend with horizontal distance increasing. The maximum magnetic intensity [TeX:] $$\mathrm{M}_{\mathrm{m}}$$ occurs at the center of the tower. Overall, for the magnetic field intensity, case 1 and case 2 are both higher than base case. The closer to the tower, the more obvious the phenomenon. The magnetic field intensity at the [TeX:] $$\mathrm{M}_{\mathrm{m}}$$ of three cases are shown in Table 5. Case 1 is [TeX:] $$1.7200 \mu \mathrm{T},$$ which is 1.46% higher than base case. Case 2 is [TeX:] $$1.7188 \mu \mathrm{T},$$ which is 1.39% higher than base case. It can be seen that online estimation of parameters have a great influence on the power frequency magnetic field.

In this paper, online estimation of transmission line parameters is achieved based on PMU. On the basis of SCADA, the parameters of any transmission line in power grid can be estimated without adding extra hardware by the least square method. The electromagnetic environment surrounding the line is analyzed and compared based on the variation of line voltage and current. The actual results show that line parameters have a great influence on the electromagnetic environment. The higher accuracy of online estimation of transmission line parameters, the higher utilization and reliability of power grid. The proposed method can be adapted to any transmission line.

He was born in Jiangsu province, China, in 1994. He received his B.E. degree in School of Software from Shandong University in 2017. He is currently pursuing his M.E. degree in electronics and communication engineering at Shandong University, China. His main research interests include power system operation and control.

He was born in Jiangsu province, China, in 1994. He received his B.E. degree in School of Software from Shandong University in 2017. He is currently pursuing his M.E. degree in electronics and communication engineering at Shandong University, China. His main research interests include power system operation and control. He obtained Bachelor’s degree in Agricultural Machinery Engineering from Shandong University of Technology. He received his master’s degree from Shandong University of Technology and now teaches at the Department of Electrical and Mechanical Engineering in Weihai Vocational College, China. The current research fields are numerical control technology and mechatronics technology.

He was born in Shandong Province, in China, on November 21, 1993. He obtained Bachelor in Electrical Engineering and Automation from Qingdao University in 2012. Now, he is a postgraduate in School of Mechanical Electrical and Information Engi-neering at Shandong University, China. He is major in electronics and communication engineering. His main research interests include power system operation and control.

- 1 A. Costa, D. Georgiadis, T. S. Ng, M. Sim, "An optimization model for power grid fortification to maximize attack immunity,"
*International Journal of Electrical Power & Energy Systems*, vol. 99, pp. 594-602, 2018.custom:[[[-]]] - 2 I. S. Okrainskaya, A. I. Sidorov, S. P. Gladyshev, "Electromagnetic environment under over head power transmission lines 110–500 kV," in
*Proceedings of International Symposium on Power Electronics Power Electronics*, Electrical Drives, Automation and Motion, Sorrento, Italy, 2012;pp. 796-801. custom:[[[-]]] - 3 E. Al-Bassam, A. Elumalai, A. Khan, L. Al-Awadi, "Assessment of electromagnetic field levels from surrounding high-tension overhead power lines for proposed land use,"
*Environmental Monitoring and Assessment*, vol. 188, no. 316, 2016.custom:[[[-]]] - 4 J. He, S. Chen, J. Guo, R. Zeng, J. Lee, S. Chang, B. Zhang, J. Zou, Z. Guan, "Electromagnetic environment analysis of a software park near transmission lines,"
*IEEE Transactions on Industry Applications*, vol. 40, no. 4, pp. 995-1002, 2004.custom:[[[-]]] - 5 M. Repacholi, "Concern that "EMF" magnetic fields from power lines cause cancer,"
*Science of the Total Environment*, vol. 426, pp. 454-458, 2012.custom:[[[-]]] - 6 I. N. Ztoupis, I. F. Gonos, I. A. Stathopulos, "Uncertainty evaluation in the measurement of power frequency electric and magnetic fields from AC overhead power lines,"
*Radiation Protection Dosimetry*, vol. 157, no. 1, pp. 11-21, 2013.custom:[[[-]]] - 7 Y. Mo, Y. Wang, F. Song, Z. Xu, Q. Zhang, Z. Niu, "Investigating the impacts of meteorological parameters on electromagnetic environment of overhead transmission line,"
*Progress In Electromagnetics Research*, vol. 70, pp. 177-185, 2018.custom:[[[-]]] - 8 Y. Wang, H. Wang, H. Xue, C. Yang, T. Yan, "Research on the electromagnetic environment of 110kV six-circuit transmission line on the same tower," in
*Proceedings of IEEE PES Innovative Smart Grid Technologies*, Tianjin, China, 2012;pp. 1-5. custom:[[[-]]] - 9 M. Sakashita, K. Nishi, S. Ito, T. Mifune, T. Matsuo, "Postcorrection of current/voltage and electromagnetic force for efficient hysteretic magnetic field analysis,"
*IEEE Transactions on Magnetics*, vol. 53, no. 6, pp. 1-4, 2017.custom:[[[-]]] - 10 L. Zhao, J. Lu, G. Wu, "Measurement and analysis on electromagnetic environment of 1000kV UHV AC transmission line," in
*Proceedings of 2012 Asia-Pacific Power and Energy Engineering Conference*, Shanghai, China, 2012;pp. 1-4. custom:[[[-]]] - 11 M. Sibanda, R. R. Van Zyl, N. Parus, "Overview of the electromagnetic environment in the vicinity of HVDC transmission lines," in
*Proceedings of 2013 Proceedings of the 10th Industrial and Commercial Use of Energy Conference*, Cape Town, South Africa, 2013;pp. 1-7. custom:[[[-]]] - 12 Z. Siroma, T. Ioroi, "Expected electrochemical impedance responses of porous electrodes based on theoretical solutions of transmission-line models,"
*Electrochemistry*, vol. 83, no. 6, pp. 425-433, 2015.custom:[[[-]]] - 13 F. Chen, X. Han, M. Li, M. Wang, M. Yang, "Tracking estimation of transmission line temperature based on PMU measurement,"
*Automation of Electric Power Systems*, vol. 33, no. 19, pp. 25-29, 2009.custom:[[[-]]] - 14 F. Chen, X. Han, K. Kang, H. Li, "Tracking of dynamic thermal rating of transmission line based on SCADA,"
*Automation of Electric Power Systems*, vol. 34, no. 5, pp. 81-85, 2010.custom:[[[-]]] - 15 J. C. Ding, Z. X. Cai, K. Y. Wang, "An overview of state estimation based on wide-area measurement system,"
*Automation of Electric Power Systems*, vol. 30, no. 7, pp. 98-103, 2006.custom:[[[-]]] - 16 Y. Xue, W. Xu, Z. Dong, Q. Wan, "A review of wide area measurement system and wide area control system,"
*Automation of Electric Power Systems*, vol. 31, no. 15, pp. 1-5, 2007.custom:[[[-]]] - 17 Y. Tohidi, L. Olmos, M. Rivier, M. R. Hesamzadeh, "Coordination of generation and transmission development through generation transmission charges: a game theoretical approach,"
*IEEE Transactions on Power Systems*, vol. 32, no. 2, pp. 1103-1114, 2016.custom:[[[-]]] - 18 C. Fang, "Studies on theory and expansion of power network state estimation,"
*PhD dissertationShandong University, Jinan, China*, 2010.custom:[[[-]]] - 19 K. Kopsidas, A. Kapetanaki, V. Levi, "Optimal demand response scheduling with real-time thermal ratings of overhead lines for improved network reliability,"
*IEEE Transactions on Smart Grid*, vol. 8, no. 6, pp. 2813-2825, 2016.doi:[[[10.1109/TSG.2016.2542922]]] - 20 S. Ge, J. Li, T. Li, H. Liu, R. Li, "Integrated analysis on reliability of power distribution network and urban road network," in
*Proceedings of the CSEE*, 2016;vol. 36, no. 6, pp. 1568-1577. custom:[[[-]]]